The laws of kashrus and forbidden foods constitute much more than 13 out of 17 mitzvos found in Parshas Shemini. Rashi, in his commentary (Vayikra 11:45) notes that throughout the Torah, the term used to describe the exodus from Egypt is "hotzeticha" - "who brought you out from the land of Egypt." Here, in summarizing the laws of forbidden foods, the Torah uses the language of "hamaaleh"- "For I am Hashem who has elevated you up out of the land of Egypt." Dbei Rabi Yishmael taught, as cited in Bava Metzia (61b), that Hashem said, "Had I not brought the people of Israel up from Egypt except to observe this law of not consuming creeping creatures, 'Dai' - I would have been satisfied." Thus the expression, "brought you up" is most appropriate, as Rashi further comments that it is "ma'alyusa hi gabaihu", an uplifting and elevating phenomenon.
We are all familiar with the teaching of the Rambam (Vayikra 11:13) that the Torah forbids the consumption of those species whose characters and natures are cruel. One absorbs the characteristics of that which they eat, and Hashem wished that his nation be possessed of a kind and sterling character. He ordained that we ingest only non-carnivorous animals, and birds that do not prey on other creatures.
The Rambam in his Egeres (letter- cited in Degel Machene Efraim, Parshas Eikev) to a community that denied the biblical concept of techiyas hamaisim (resurrection of the dead) writes that the effect of the dietary laws of the Torah is that they purify man's thought process. This enables mortal man, entrenched in the physical world, to comprehend and absorb the highest level of spirituality- Hashem's Torah. Commensurate with ones scrupulous attention to the details and laws of kashrus is one's ability to grasp greater and deeper lessons from the Torah. A significant factor contributing to the success of the Ta'naim and Amoraim (the scholars of the Talmud) was the observance of these laws. The converse, continues the Rambam, is that if one disregards the dietary laws of the Torah, you will be faced with a lack of clarity and comprehension of Torah principles. This in no small measure contributed to a community's denial of techiyas hamaysim in Rambam's day.
The phrase "you are what you eat" is then understood as not only regarding one's character, but your intellectual ability to understand Hashem's Torah. This may be further clarified by the classification of the Kuzari (Part 5) of all physical entities into four categories: minimal, plant life, animals, and man. To this he adds the Jew as a fifth phenomenon. Just as there is a marked difference between the highest form of plant life (the cedar tree) and the lowest form of animal life (the ant), similarly there is a distinction between the Jew and the rest of mankind. The soul of the Jew differs qualitatively from that of mankind, as we recite in the blessings after the Torah portion has been read, "who has given us the Torah of truth, and implanted eternal life within us". Kashrus in no small measure helps us attain this eternal life.
Finally it is interesting to note the blessing of Borei Nefashos, which is recited after eating any food for which neither Birchas Hamazon (Grace After Meals) nor the Three Faceted Blessing applies, such as fruits, vegetables, and beverages other than wine. This blessing thanks Hashem for creating Man, and indeed all species, lacking. All living organisms need nourishment. We continue to thank Hashem for providing this life-sustaining nourishment. The blessing concludes, "blessed is He the life of the worlds". The word "worlds" is in the plural because His sustenance provides us with this world, and the realization thereof that He sustains us, and with our kosher diet, provides us with our worthiness of and entry into the next world.
This is Rashi's theme at the end of Parshas Shmini (11:44) "just as I am holy, for I am the Lord your God, make yourselves holy, for I will sanctify you above and in the world to come." There is much more to kashrus than do's and don'ts!